Applications utilizing electrical modules which generate an appreciable amount of heat, usually require that heat dissipation paths are designed in to prevent overheating of these modules. One popular solution is to locate a heat sink, such as a metal plate, at or near the site of the heat generating module, and providing a thermal path for heat to travel from this heat sink to other heat dissipating locations. For example, a relatively large power amplifier can be implemented on a substrate, and this substrate is mounted on a heat sink, and the heat sink is mounted on another substrate such as a printed circuit board. A heat dissipation path could be created by thermally connecting the heat sink to the frame of chassis of the host device. Leads would provide the electrical connection between the substrate containing the power amplifier and the printed circuit board. Similar configurations are quite common in the art.
Despite some of the obvious manufacturing advantages of using leadless surface mountable modules, the use of leads has persisted to provide electrical connection between the module containing the heat generating electrical components and the general circuitry for the application. This results from the traditional design of placing the heat, sink, which can be rather bulky, directly under the module, so that the electrical connections must be routed around the heat sink. Thus, leads are often used to accomplish this routing.
However, there are several problems which are inherent in the use of leaded electrical modules in the assembly of electronic circuitry. One such problem is that of lack of planarity, i.e., where the ends of the leads are not all on the same level or plane. Lack of planarity may prevent proper electrical connection between the component and the supporting substrate, thus affecting the ease of manufacture and the reliability of the assembly. Automatic placement of leaded components can also be difficult, depending on the size and orientation of the module, and hand placement may be necessary. Some applications, such as those involving wireless communications, require shielding of certain electrical modules to minimize electrical interference and spurious radiation emissions from the module. With leaded modules, the shields need openings to accommodate the leads, or alternatively, the shields need to be shaped to encompass the leads. Assuming the application is implemented on a printed circuit board (PCB), the PCB layout must accommodate these shields and this can reduce the space available for the other circuit components.
The problems described thus far are particularly prevalent with the use of power amplifiers in the wireless communications industry. The packaging of high output power amplifiers or other high energy modules with large heat dissipation requirements have traditionally relied on leads to electrically connect the module to the printed circuit board. However, the demand for increase product quality and reduced manufacturing costs requires new solutions to the packaging design for these modules. As such, it is desirable to eliminate the leads for these electrical modules while retaining the heat dissipation characteristics of existing packages.